Genki started his professional career in shoot wrestling promotion Pancrase, defeating Kosei Kubota by unanimous decision in his first fight. He joined Sanae Kikuta's Grabaka team to further develop his grappling skills.

Sudo became well known for his particularly flashy choreographed ring entrances that often included costumed dancers. One entrance featured Sudo doing the robot and operating levers that released a column of smoke from the top of his head while wearing a Kentucky Fried Chicken bucket as a hat and a white plastic mask, in an homage to the musician Buckethead.

Sudo had his debut in Ultimate Fighting Championship at UFC 38, facing Leigh Remedios. Making his entrance in a kimono and a tengu mask, Sudo showed his personal syle by dancing and throwing spin kicks to open the match, eventually launching a flying triangle choke attempt which lasted for most of the round. At the second round, Genki threw Remedios with a hip throw and locked a rear naked choke, making him tap out. The Japanese wrestler then posed with a flag of all the nations and proclaimed his catchphrase of "We Are All One" for a crowd pop.

He returned at UFC 42 against Duane Ludwig. Again Sudo showed his theatrical side, walking backwards towards Ludwig and doing the robot dance before taking him down. However, despite his initial domination, the Japanese started receiving damage while standing, failing in a rolling kneebar and several takedown attempts. Sudo came back at the last round, bloodying Ludwig's nose with punches for a possible doctor stoppage, but his opponent returned the favour and dominated the end for a unanimous decision. Duane mocked Sudo with a crane kick pose after the end of the fight.

Sudo's last fight in UFC would be against the debuting Mike Brown in UFC 47. Brown tried to capitalize in Sudo's confusing moves by rushing him against the fence, managing to slam him on the mat, but Sudo then locked a triangle choke and transitioned into an armbar for the tap out.

In 2008, he accepted the position of Manager for Takushoku University’s wrestling team. In the 2009 Eastern Japan University League Games, the 2009 All Japan University Greco-Roman Championship Tournament, and the 2010 All Japan University Wrestling Conference, he was awarded the prize for Best Manager. In addition, he led the team to victory in the 2010 All Japan Student Wrestling Championship, and in his second year as manager Takushoku University was victorious at all four of the biggest student wrestling tournaments. In 2010, he was made the Japanese representative manager for the World University Championship.

A fighter with unorthodox striking and grappling ability, he has won fights by flashy knockout in both mixed martial arts and kickboxing. Among the unusual techniques that he favors and can use effectively are the spinning backfist, flying triangle choke and flying armbar, as well as dancing and turning his back to opponents in order to taunt or distract them.

Sudo is a practicing Buddhist.[13] He married on November 22, 2007, but got divorced in 2014.

Sudo has written eight books and has started an amateur baseball team for people 30 and over.

On August 1, 2009, Genki Sudo and his office made an official statement to say information on Wikipedia was wrong. According to their statement, the bout between Sudo and Tiki Ghosn was originally declared a draw which was overturned after Sudo’s corner man, Bas Rutten, objected, at which point Sudo was declared the winner and given a medal.[14][15]

On January 25, 2010, Genki took the entrance examination of Takushoku University Graduate School and he was admitted to the school on January 29. He entered the Local Government Course (Master’s Program) of the Graduate School of Local Government.[16]